The present disclosure relates to motor position detection systems, and particularly to systems for detecting and reporting potential defects in a coding wheel used to determine the position of a motor.
Coding wheels are used in motor regulation to detect speed and also rotational, or angular, position of the motor. A coding wheel for position detection includes one or more index markers and/or one or more sets of uniformly sized and spaced angular step markers. The coding wheel spins while the motor is operating. A photo-detector projects a beam onto the coding wheel and detects the markers as they pass through the beam. A decoding computer then interprets the detection information to determine the motor position; detection of the index marker may indicate a complete revolution of the motor, while each angular step marker corresponds to a degree increment of the angular position.
A lack of accuracy in the detected angular motor position can lead to a loss of motor performance and can even cause damage to the motor. Coding wheel defects can, for example, come from dust or dirt on the coding wheel that prevents reflection of the beam back to the photo-detector or creates a parasitic reflected beam (i.e., from glossy or reflective dust) detected by the photo-detector, or from damage to the coding wheel that impacts the reflection of the beam back to the photo-detector. These defects induce an inaccurate change of step count between index detections, which in turn causes the decoding computer to record the wrong motor position and speed during rotation. It is useful to be able to detect various cases of coding wheel and/or other detection defects, and to generate alerts for maintenance of the detection system, such as cleaning or repairing the coding wheel, is needed.